1. Field of the Invention
The invention relates to a prosthetic joint socket member, in particular for a hip prosthesis. More particularly, this invention relates to an acetabular cup.
2. Description of the Prior Art
Prostheses for the replacement of hip joints have been used for many years. these prostheses usually includes s stem portion on which a spherical ball is mounted and an acetabular portion or socket member for implantation is in the natural acetabulum. Alter naively, the acetabular prosthetic cup may receive the ball of the natural femur which may be may not be resurfaced.
From German patent specification 23 01 801, it is known to make a cup member from a hollow outer shell and an inner shell. The inner shell has a recess for accommodating the ball. Due to the forces acting on the cup member, the cup member may become loosened in the bone. European patent specification 0 303 006 discloses a method to provide the outer surface of the cup member with small balls in order to improve the in growth of the prostheses int h bone material.
european patent specification 0 329 019 discloses a cup member consisting of an outer an an inner shell to be screwed into the hip bone. The outer hollow shell has circular or elongated openings permitting spongiosa or loose bone substance to be introduced into and securely held in the intermediate space between outer and inner shell. The introduction of this material can be carried out during the operation and thereafter ensures growth there into of a new wrong bone substance. The outer surface of the outer shell has thread portions interrupted by grooves which form a tapping thread.
The affixing of the joint socket member is predominantly affected by screwing the socket body portion into the bone substance by means of the self-tapping screw thread, and the anchoring of the prosthesis is increased by the in growth of bone material.